Answer: Choice B
Why is this? It's because each time x goes up by 2, y is also increasing by 2. The rate of change is constant. I'm treating n as x, and C as y.
Another way to see why we have a linear function is to pick any two points from that table, and apply the slope formula
m = (y2-y1)/(x2-x1)
You should find that no matter which two rows you pick, you should get a slope of 1.
Lastly, you can plot the three points from the table to find they all are on the same straight line as shown below. So there are at least 3 different ways to justify choice B as the answer.
Side note: The equation of the line is y = x-7, which then translates over to C = n-7.